AIR POLLUTION SOURCES 99
Part 1. Pollutant Emissions (continued)Pollutant types Sources and abundance Abatement and control
3) Nickel is used extensively as a catalyst
(for i.e. Raney Nickel) used in hydrogenation
of organic compounds, dehydrogenation of
organic compounds, aging of liquors, etc.
4) Aviation and automobile engines burning fuels
containing nickel concentrations range from
1 to 10% nickel.
5) Burning coal and oil-nickel in ash varies from 3
to 10,000 mg/g
6) Incineration of nickel products.
d. CADMIUM: Is a relatively rare metal which is not
found in a free natural state. It is obtained from zinc,
lead, copper and other ores that contain zinc minerals.
Pollution exists as fumes, and vapors. The major use
of cadmium is for electroplating iron and steel.
The most common cadmium compounds and their uses
are:
1) Electroplating—cadmium cyanide, Cd(CN 2 ), and
cadmium acetate, Cd(CH 3 COO) 3.
2) Photography and dyeing—cadmium chloride, CdCl 3.
3) Manufacture of phosphors, glass in nuclear reactor
controls.
4) Manufacture of electrodes for storage batteries—
cadmium hydroxide Cd(OH) 3.
5) Cadmium iodide, CdI 2 , electrode-position of Cd,
manufacturing of phosphors.
6) Cadmium oxide—CdO.
In phosphores, semi-conductors, manufacture of
silver alloys.
7) Cadmium selenide—CdSe.
In Photoconductors.
8) Cadmium sulfate—CdSO 4.
In electrodeposition Cd, Cu,
and N.
9) Dimethylcadmium Cd(H 3 ) 2
In organic synthesis.Major sources are: (See Table 17)
1) Mining—Since no ore is mined solely for
cadmium recovery, emissions of cadmium dust
ore vapors are those that occur during mining
and concentration of zinc-bearing ores.
2) Metallurgical processing—most of the
atmospheric emissions occur during the roasting
and sintering of zinc concentrates as impurities
are removed. Cadmium is volatized and
condensed to be collected as dust in baghouses
or electrostatic precipitators. Lead and copper
smelters also process concentrates containing
cadmium.
3) Reprocessing—emissions occur during
electroplating, manufacturing.
4) Consumptive uses—include use of rubber
tires, motor oil, fungicides and fertilizers.
5) Incineration and ether disposal gaseous
emissions will occur when scrap metal is
melted to make new steel.
6) Cadmium used in plastics and pigments.
NATURAL OCCURRENCE:
The concentration of cadmium is almost always in
direct proportion to that of zinc. The cadmium
to zinc ratio varies from about 0.0002 to 0.002.
With respect to the cadmium concentration
percentage of the earth’s crust, it is roughly
0.000055. Small concentrations of cadmium
have been estimated in soil and sea water.
MAN-MADE OCCURRENCE
Mining—2 lbs are emitted per ton of cadmium
mined usually as wind loss from tailings.
Metallurgical processing.General control procedures for the
prevention of air pollution by
dust, fumes, and mists
applicable to the metal refinery
alloying, and machining
industries are considered
suitable to these processes in
the cadmium industry.
— Copper mining and smelting:
addition of bag filters and
cyclones added to increase
the recovery of cadmium.
— Use of flue systems to direct
the flow of gases to proper
receptacles.e. ARSENIC: a brittle, very poisonous chemical element,
found widely distributed over the earth’s crust. It is
most often found with copper, lead, cobalt, nickel,
iron, gold and silver.
Arsenic is commonly found as a sulfide, arsenide,
arsenite, or arsenate.Major sources: (See Table 18)
a) Smelters processing copper, zinc, lead and
gold—arsenic is recovered as by product.
b) Cotton ginning and the burning of cotton trash.
c) Use as a pesticide (DDT).
d) Combustion of coal.
e) Incineration.
Possible sources are: (See Table 18) manufacturing
of glass—arsenic pentoxide, As 2 O 3 , arsenic
trisulfide. As 2 S 3 manufacturing of ceramics—
arsenic trichloride, As 2 Cl 3a) Use of air cleaning devices to
remove particulates from
smelters and cotton gins.
Equipment must operate at
temperatures low enough to
condense arsenic fumes
( 100 °C)
—Electrostatic precipitators
—Cooling flues
— Bag houses, especially those
using wet scrubbing vacuum
pumps instead of fabric
filters.
b) No methods available to control
emissions produced by burning
cotton trash.
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